Iowa Code § 701.4: Insanity.

A person shall not be convicted of a crime if at the time the crime is committed the person suffers from such a diseased or deranged condition of the mind as to render the person incapable of knowing the nature and quality of the act the person is committing or incapable of distinguishing between right and wrong in relation to that act. Insanity need not exist for any specific length of time before or after the commission of the alleged criminal act. If the defense of insanity is raised, the defendant must prove by a preponderance of the evidence that the defendant at the time of the crime suffered from such a deranged condition of the mind as to render the defendant incapable of knowing the nature and quality of the act the defendant was committing or was incapable of distinguishing between right and wrong in relation to the act.